Abstract: An air distribution unit comprising a housing and louvered inlet and outlet grilles. The housing forms an interior space, an inlet for conducting air into that interior, and an outlet for discharging air from the air distribution unit; and the inlet and outlet grilles are located in the inlet and outlet of the housing, respectively. These grilles have identical shapes and identical sizes and each grille includes a multitude of parallel louvers that are held in fixed positions in the grille. Moreover, the inlet grille has first and second positions to help direct air into the interior of the housing at first and second inlet angles respectively, and the outlet grille has first and second positions for directing air from the interior of the housing at first and second outlet angles respectively.